Male rat with breathing issue.

One of my Russian Blue males has been acting a bit strange lately. He shakes as he breaths. He is a video:

http://www.youtube.com/watch?v=Hu_XE...yer_detailpage

I don't know if it would be considered labored breathing, but his whole body shakes as he breathes. He has lost some weight and is a little lethargic (in that he doesn't fight as much being picked up, maybe is just overall weakness). But he will still take treats so not a total loss of appetite. His normal diet is Native Earth 4018 and once in awhile Kix as treats.
I thought at first maybe some kind of RI but there is no red discharge around his eyes or nose.

Has anyone seen anything similar?

Try giving him some Ensure or soak some rodent block in Ensure. It helps give him a boost in energy. It could be RI even though he's not showing any nasal discharge.

Could you hear any clicking when he breaths?
If it is RI, you can buy Tetracycline powder from the fish section of a petstore. You can add this powder to their water. It won't harm any of your other rats or the snakes you feed them too. It will clear up any potential RI in a week or two.
The Tetracycline usually comes in packets of 50mg. And that can be added to a 16oz water bottle. (or equivalent ratio)

No clicking or any other sounds when he breaths.

I'll pick up some Ensure. He loves Kix, would Kix soaked in Ensure be ok?

Also, I forgot to mention his age is about 10 months (although I don't think that matters).

He's definitely sick. You should not be able to see him breathing that hard, and at 10 months, he should not be losing weight. He also looks a little unkempt, like he's not grooming himself so well.

All these things would make me take him to a vet to get him checked out, especially since it looks like he's a breeder. You don't know if he has something contagious that can spread to all the other rats.